How does the disc obtain nutrition, specifically in the nucleus pulposus?

How does the disc obtain nutrition, specifically in the nucleus pulposus?

• A. Diffusion
• B. Osmosis
• C. Imbibition
• D. Filtration

Answer: (C)

Nutrients reach the avascular nucleus pulposus by diffusion from the vascularized vertebral endplates, but the key to bringing fluid and dissolved nutrients into the disc is imbibition. The proteoglycan-rich matrix of the nucleus pulposus creates a strong osmotic pull that draws water into the tissue, along with the solutes it contains. This osmotic-driven water uptake is imbibition, and it sets up the environment and medium for solutes to diffuse through the disc tissue to cells. Under load, fluid is pushed out, and when the load decreases, imbibition brings water back in, helping sustain nutrition and hydration. Filtration isn’t the primary mechanism here, and diffusion describes solute movement rather than the initial uptake of fluid into the disc; osmosis is related but the term imbibition best captures the disc’s water uptake driven by osmotic forces.

Nutrients reach the avascular nucleus pulposus by diffusion from the vascularized vertebral endplates, but the key to bringing fluid and dissolved nutrients into the disc is imbibition. The proteoglycan-rich matrix of the nucleus pulposus creates a strong osmotic pull that draws water into the tissue, along with the solutes it contains. This osmotic-driven water uptake is imbibition, and it sets up the environment and medium for solutes to diffuse through the disc tissue to cells. Under load, fluid is pushed out, and when the load decreases, imbibition brings water back in, helping sustain nutrition and hydration. Filtration isn’t the primary mechanism here, and diffusion describes solute movement rather than the initial uptake of fluid into the disc; osmosis is related but the term imbibition best captures the disc’s water uptake driven by osmotic forces.